The present invention relates to a mechanism to be adapted in an image recording apparatus for correcting a bent recording sheet.
Conventionally, there have been known electrophotographic image recording apparatuses, wherein a latent image is formed by exposing a uniformly charged photoconductive material provided on the circumferential surface of a photoconductive drum, the latent image is developed (toner image is formed) by being adhered with toner, and the toner image is transferred onto a recording sheet and fixed by a fixing unit. One of such image recording apparatuses is an electrophotographic printer such as a laser beam printer which prints image data onto a recording medium. A continuous form recording medium such as a so-called fan-fold paper provided with feed holes and perforated tear lines has been conventionally used in such a printer.
The perforated tear lines are provided at the boundary of each page of the fan-fold paper, and the fan-fold paper can be cut off along the perforated tear line. Before the fan-fold paper is introduced in the printer, it is folded alternately in an opposite direction at the tear lines.
Incidentally, a printer using the continuous recording medium such as the fan-fold paper preferably starts printing from the position of the continuous paper spaced apart from the perforated tear line thereof (i.e., spaced apart from the leading edge of a page) by a predetermined distance, and stops the printing at the position having a predetermined distance to the perforated tear line defined along the trailing edge of the page. In this case, when the printing operation has been completed, the perforated tear line of the fan-fold paper is located in the vicinity of the image transfer position of a photoconductive drum.
In the arrangement of the electrophotographic image forming process, an exposure unit, development unit and transfer unit are disposed around the photoconductive drum, and these units operate as the photoconductive drum rotates, so that an image is transferred when the exposed portion of the photoconductive drum faces a transfer position of the fan-fold paper. Therefore, to ensure that the portion of the photoconductive drum at which the beginning of the exposure is located coincides with the position of the fan-fold paper which is spaced apart from the perforated tear line thereof by a predetermined distance (i.e., to start printing from the position of the fan-fold paper spaced apart from the perforated tear line thereof by the predetermined distance) at the start of the printing, a print start position must be adjusted by relatively moving (rotating) the photoconductive drum with respect to the fan-fold paper before the printing (transferring) is started.
Nevertheless, since the fan-fold paper is alternately folded along the perforated tear lines thereof to an opposite direction, as described above, the fan-fold paper tends to be bent in the direction it has been folded when it is fed in the printer. Thus, if the fan-fold paper tends to bend in the direction projecting toward the photoconductive drum along the perforated tear line at the transfer position of the photoconductive drum (if the fan-fold paper is bent such that the back sides thereof tend to face to each other), the perforated tear line abuts against the circumferential surface of the photoconductive drum, and thus the fan-fold paper is stained by residual toner remaining on the surface of the photoconductive drum when the photoconductive drum is relatively moved, or rotated with respect to the fan-fold paper to correspond to a print start position before the printing is started (black stripes are made along a axial direction of the photoconductive drum).